What is the ruling on a man marrying his father's wife's sister from nursing, who shared nursing with his sister from her mother, and is his wife considered his sister from nursing?

If the reality is as stated, then Ghaytha is your sister through suckling; because your father is one, and each of you suckled from milk that resulted from his cohabitation. Therefore, it is not permissible for you to marry her, and you must separate from her and annul the marriage. The children are attributed to you due to the شبهة (semblance of legality). This ruling of prohibition due to the milk of the husband (fahl) is in accordance with the evidence, more cautious, and clears one's conscience.